What is it and cause

[charles mann]

I was out burning grass from around the hard to reach areas around my log pile. A black walnut was smoldering under the bark. I peeled most of the bark off to ensure the embers were out. 

As i peeled the bark off, i noticed bird beak looking formations all along the log. No pics, got to dark by the time i got all embers/coals out and ensured no lil accidents occur after bed time. 

Any ideas why they formed or what caused them? Could they cause abnormal character or defects?